Garmin GPS 24xd Receiver and Antenna Technical Reference for Garmin NMEA 2000 - Page 10

Middle-Powered NMEA 2000 Network Designed Correctly Drop cable Length = 2 m Power cable Length = 2 m Drop cable Length = 4 m Drop cable Length = 6 m Backbone cable Length = 10 m Backbone cable Length = 6 m When the NMEA 2000 network is redesigned with the power source in the center, calculate the voltage drop in both directions. If the T-connector to which you connect the power source is connected directly to another Tconnector (as shown in this example), use the LEN from the device connected to that T-connector as part of the calculation for both directions. Voltage Drop to the Left of the Power Connection Resistance × Distance × Load × 0.1 = Voltage drop 0.053 × 14 (2 + 10 + 2) ×4 × 0.1 = 0.30 Vdc Voltage Drop to the Right of the Power Connection Resistance × Distance × Load 0.053 × 12 (2 + 6 + 4) × 12 (5 + 7) × 0.1 × 0.1 = Voltage drop = 0.80 Vdc Power Isolation Some NMEA 2000 devices, such as a boat engine, provide power to the NMEA 2000 network. In some cases, this may be sufficient to provide the appropriate power to the network, but in other cases this may result in providing power to the network in two places, and could result in unexpected behavior or may damage other connected devices. To accommodate two power connections to the network, you can install a power isolator (010-11580-00) in the backbone to when connecting devices to the network that also provide power. The power isolator allows data communication, but does not allow power to pass through. 10